Which blue-colored liquid is obtained upon reacting equimolar amounts of two gases at $-30\,^{\circ}C$?

Discuss the trends in chemical reactivity of group $15$ elements.

Which of the following is not known?

Which of the following is the most suitable drying agent for ammonia gas?

Which of the following is the structural formula of hypophosphorous acid?

On reaction with $Cl_2$,phosphorus forms two types of halides $A$ and $B$. Halide $A$ is a yellowish-white powder,while halide $B$ is a colourless oily liquid. Identify $A$ and $B$ and write the formulas of their hydrolysis products.